/**
 * u51.com Inc.
 * Copyright (c) 2004-2015 All Rights Reserved.
 */
package com.jeestudio.utils;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * 
 * @author byshome
 * @version $Id: MD5Utils.java, v 0.1 2015年8月4日 下午2:39:13 byshome Exp $
 */
public class MD5Utils {
    /**
     * 默认的密码字符串组合，用来将字节转换成 16 进制表示的字符,apache校验下载的文件的正确性用的就是默认的这个组合
     */
    protected static char          hexDigits[]   = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c',
            'd', 'e', 'f'                       };
    protected static MessageDigest messagedigest = null;
    static {
        try {
            messagedigest = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
    }

    public static String getFileMD5String(File file) throws IOException {
        InputStream fis;
        fis = new FileInputStream(file);
        byte[] buffer = new byte[1024];
        int numRead = 0;
        while ((numRead = fis.read(buffer)) > 0) {
            messagedigest.update(buffer, 0, numRead);
        }
        fis.close();
        return bufferToHex(messagedigest.digest());
    }

    public static String getInputStreamMD5String(InputStream fis) throws IOException {
        byte[] buffer = new byte[1024];
        int numRead = 0;
        while ((numRead = fis.read(buffer)) > 0) {
            messagedigest.update(buffer, 0, numRead);
        }
        fis.close();
        return bufferToHex(messagedigest.digest());
    }

    public static String getStringMD5(String str) {
        byte[] buffer = str.getBytes();
        messagedigest.update(buffer);
        return bufferToHex(messagedigest.digest());
    }

    public static byte[] getMD5(String str) {
        byte[] buffer = str.getBytes();
        messagedigest.update(buffer);
        return messagedigest.digest();
    }

    public static byte[] getMD5(byte[] b) {
        messagedigest.update(b);
        return messagedigest.digest();
    }

    public static String bufferToHex(byte bytes[]) {
        return bufferToHex(bytes, 0, bytes.length);
    }

    public static byte[] hex2Bytes(String src) {
        int i = src.length() / 4;
        byte[] data = new byte[i];
        for (int j = 0; j < i; j++) {
            String str = src.substring(j * 4 + 2, (j + 1) * 4);
            data[j] = (byte) Integer.parseInt(str, 16);
        }
        return data;
    }

    public static void main(String[] args) {
        System.out.println(hex2Bytes("\\x00\\x00\\x00\\x00\\x2c\\xe0\\x44\\xa3"));
    }

    private static String bufferToHex(byte bytes[], int m, int n) {
        StringBuffer stringbuffer = new StringBuffer(2 * n);
        int k = m + n;
        for (int l = m; l < k; l++) {
            appendHexPair(bytes[l], stringbuffer);
        }
        return stringbuffer.toString();
    }

    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
        char c0 = hexDigits[(bt & 0xf0) >> 4];// 取字节中高 4 位的数字转换
        // 为逻辑右移，将符号位一起右移,此处未发现两种符号有何不同
        char c1 = hexDigits[bt & 0xf];// 取字节中低 4 位的数字转换
        stringbuffer.append(c0);
        stringbuffer.append(c1);
    }
}
